Process and apparatus for continuously producing slub yarn

ABSTRACT

A slub yarn having a hand spun silk yarn-like appearance and feel to the hand is continuously produced from a multifilament yarn by feeding the multifilament yarn into a reduced pressure region formed in a hollow column at a predetermined feed rate while vigorously sucking air from the atmosphere through the region, agitating the multifilament yarn by the sucked air current to convert portions of the yarn into slubs consisting of portions of the yarn and/or the individual filaments entangled, intertwined, looped, bent and/or folded by action of the sucked air vortex or turbulent current, and delivering the resultant slub yarn from the reduced pressure region at a delivery rate lower than the feed rate.

United States Patent Adachi et al.

[ Oct. 28, 1975 PROCESS AND APPARATUS FOR CONTlNUOUSLY PRODUCING SLUB YARN Assignee: Mitsubishi Rayon Co., Ltd., Japan Filed: Jan. 30, 1974 Appl. No.: 437,796

US. Cl 57/34 B; 28/].4; 28/72.!2; 57/140 BY; 57/140 J; 57/157 F Int. Cl. DOZG 1/16; D02G 3/04; DOZG 3/34;

3,433,007 3/1969 Myers 57/140 J 3,474,613 l0/l969 Joarder et al. 57/34 B Primary ExaminerJohn Petrakes Attorney, Agent, or Firm-Armstrong, Nikaido & Wegner [57] ABSTRACT A slub yarn having a hand spun silk yarn-like appearance and feel to the hand is continuously produced from a multifilament yarn by feeding the multifilament yarn into a reduced pressure region formed in a hollow column at a predetermined feed rate while vigorously sucking air from the atmosphere through the re gion, agitating the multifilament yarn by the sucked air current to convert portions of the yarn into slubs D026 3/40 consistin g of port1ons of the yarn and/or the 1nd1v1dual [58] Fleld of s 57/34 157 140 filaments entangled, intertwined, looped, bent and/or 5 H 0 folded by action of the sucked air vortex or turbulent current, and delivering the resultant slub yarn from [56] References C'ted the reduced pressure region at a delivery rate lower UNITED STATES PATENTS than the feed rate.

3,116,589 1/1964 Edwards et al. 57/157 F 3,122,816 3/1964 Rhoden 28/72.12 32 Clams 11 D'awmg F'gures US. Patent Oct.28, 1975 Sheet20f3 3,914,929

US. Patent Oct. 28, 1975 Sheet 3 of3 3,914,929

PROCESS AND APPARATUS FOR CONTINUOUSLY PRODUCING SLUB YARN The present invention relates to a process and apparatus for producing a multifilament fancy yarn, more particularly, it relates to a process and apparatus for continuously producing a multifilament slub yarn suitable for forming a silk shun tung-like fabric.

The term silk shun tung used here refers to a handmade fabric of a hand spun silk yarn which is uneven in thickness. This hand spun silk yarn has slubs and knots formed thereon.

According to the general accepted idea, the principal purpose of weaving and knitting is to provide a fabric having a desired appearance and feel to the hand. In this regard, the silk fabric called shun tung received universal commendation when it appeared because of its grain, elegant and naive appearance and feel to the hand.

There have been attempts to produce an artificial filament fancy yarn having a hand spun silk yarn-like appearance and feel. in the most conventionally used of these attempts the yarn is produced, using a fancy twister, by intermittently twining a multifilament yarn about a multifilament core yarn to form slubs and then, bonding the slub-forming yarn and the core yarn with a multifilament bonding yarn. in the conventional method stated above, the resultant fancy yarn feels hard to the hand because the component yarns are firmly twisted. Accordingly, the fabric made of the conventional fancy yarn feels too hard even though the fabric has the shun tung-like appearance.

It is known from other attempts that the hand spun silk yarn-like fancy yarn is produced by feeding at least one multifilament yarn intermittently and at least one multifilament yarn continuously into a zone blown by a fluid jet. By the action of the fluid jet, the individual filaments in the yarns are entangled and, intertwined with each other. That is, the continuously fed yarn is converted to slubs formed on the intermittently fed yarn.

However, the known process stated above has the following disadvantages.

1. High cost in production, because two or more component multifilaments are necessary for producing only one fancy yarn.

2. Very complicated production apparatus, because one or more component yarns must be intermittently fed to the twister.

3. Undesirable formation of a wood grain-like pattern or tortoise shell pattern on the fabric, because the slubs are fomed on the yarn at fixed intervals.

4. Low efficiency in energy utilization of the fluid jet.

5. Low production velocity.

An object of the present invention is to provide a process and apparatus for continuously producing slub yarns having a hand spun silk yarn-like appearance, a soft feel to the hand and high processability, with high efficiency and at a high production velocity.

The other object of the present invention is to provide a process and apparatus for continuously producing slub yarns having slubs firmly bundled on the yarn, using a simple slub-forming means.

The above-stated objects can be accomplished by the process and apparatus of the present invention. According to the process of the present invention, a slub yarn is continuously produced by the steps of providing a reduced pressure region by sucking air from the atmosphere through the region, feeding a multifilament yarn into the reduced pressure region at a predetermined feed rate while continuing to suck the air through the reduced pressure region, agitating the fed yarn within the reduced pressure region by the action of the sucked air current to convert portions of the fed yarn into slubs consisting of entangled, intertwined and/or folded portions of said yarn and/or individual filaments in said yarn, and delivering the resultant slub yarn from the reduced pressure region at a delivery rate lower than the feed rate.

The apparatus of the present invention comprises a slub-forming device comprising a hollow column having a yarn supply end plate with a yarn supply hole formed thereon and a yarn delivery end plate with a yarn supply hole formed thereon, means for feeding a multifilament yarn into said slub-forming device at a predetermined feed rate, and means for delivering the slub yarn from said slub-forming device at a delivery rate lower than the feed rate, the slub-forming device being connected at its periphery to a vacuum device through an air suction pipe.

When the multifilament yarn is fed into the reduced pressure region formed in the slub-forming device at a feed rate higher than the delivery rate, the multifilament yarn is agitated by the action of air stream vigorously sucked from the atmosphere through the yarn supply and delivery holes into the reduced pressure region. As a result of the agitation, portions of the multifilament yarn and/or portions of individual filaments in the yarn are entangled, intertwined, folded and/or bent to form the slubs on the yarn. The portions of the yarn are converted into the slubs in response to the difference between the feed rate and the delivery rate. That is, not all of the multifilament yarn is converted into slubs. While the multifilament yarn fed into the reduced pressure region is agitated by the action of the sucked air steam and vigorously moves throughout the region, some portions of the yarn or the individual filaments are rubbed with other portions of the yarn, other filaments or the inside wall surface of the slub-forming device so as to produce static electricity thereon. This static electricity generated on some portions of the yarn or individual filaments can promote the entanglement, intertwining bending and/or folding of the yarns and/or the individual filaments. The generation of the static electricity is effected irregular and at unfixed intervals of time on portions of the yarn or the individual filaments. This causes irregular distribution and unfixed lengths and thicknesses of the slubs.

The reduced pressure region is formed in a slubforming device by vigorously sucking air with a vacuum device from the atmosphere through the yarn supply hole, yarn delivery hole and the slub-forming device. The sucked air generates vigorous vortexes or turbulent currents in the slub-forming device. The vigorous air vortexes or turbulent currents can agitate the multifilament yarn to open it into separate individual filaments and entangle, intertwine, bend and/or fold the individual filaments. The type and amount of the air vortexes or turbulent currents are in response to the 3 and then, the slub yarn is delivered upward from the region. However, the yarn may travel downward or laterally.

The features and advantages of the present invention will be apparent to persons acquainted with this type of fancy yarn upon reading the following descriptions and referring to the accompanying drawings, in which:

FIG. 1 shows an explanatory view of an embodiment of the apparatus of the present invention;

FIG. 2 shows an explanatory cross-sectional view of an embodiment of a slub-forming device with an air suction pipe, usable for the apparatus of the present invention;

FIG. 3 is an explanatory cross-sectional view of an embodiment of a slub-forming device with an air suction pipe and an air permeable partition disposed in the slub-forming device, usable for the apparatus of the present invention;

FIG. 4 is an explanatory cross-sectional view of an embodiment of a slub-forming device with an air suction pipe and an air permeable partition located in the air suction pipe, usable for the apparatus of the present invention;

FIG. 5 is an explantory cross-sectional view of an embodiment of a slub-forming device with an air suction pipe, a yarn storage inner tube disposed in a yarn supply end portion of the slub-forming device and an air suction member located in a yarn delivery end portion of the slub-forming device, usable for the apparatus of the present invention;

FIG. 6 shows a cross-section of the air suction member shown in FIG. 5, along line VI-VI in FIG. 5;

FIG. 7 shows a cross-section of the slub-forming device shown in FIG. 5, along line VII-VII in FIG. 5;

FIG. 8 is an explanatory cross-sectional view of an embodiment of a slub-forming device with an air suction pipe, an air suction member, a yarn storage inner hollow column and an air vortex inner hollow column disposed between the air suction member and the yarn storage inner hollow column, usable for the apparatus of the present invention;

FIG. 9 shows a cross-section of the slub-forming device shown in FIG. 8, along line IXIX in FIG. 8, and;

FIGS. 10 and 11 respectively show an explanatory view of an embodiment of the slub yarn produced in accordance with the present invention.

The process of the present invention may be carried out by the apparatus as shown in FIG. 1. In the drawing, a multifilament yarn 1 is taken from a yarn supply package 2 by means of a pair of feed rollers 3a and 3b and fed into a slub-forming device 4 at a predetermined feed rate. The slub-forming device 4 is connected to a vacuum device 5 through an air suction pipe 6 to define therein a reduced pressure region. When the vacuum device 5 is actuated, the reduced pressure region is formed in the slub-forming device 4, and air is vigorously sucked from the atmosphere into the slub-forming device 4. The sucked air produces a vigorous vortex or turbulent current in the slub-forming device. By the action of the sucked air current, the multifilament yarn is converted into a slub yarn 7 having slubs 7a while the multifilament yarn is in the slub-forming device 4. The slub yarn 7 is removed from the slub-forming device 4 by means of a delivery roller 8 at a delivery rate lower than the feed rate, and wound up into a yarn take up package 9.

As stated above, while the multifilament yarn 1 is in the slub-forming device 4, the yarn l is vigorously agitated by the action of the air vortex or turbulent current. This agitation results in looping, bending, folding and opening of the multifilament yarn and entanglement, intertwining, looping, bending and folding of the separated individual filaments. These movements of the yarn and individual filaments cause the irregular formation of slubs on the yarn. That is, some portions of the multifilament yarn are converted to slubs having irregular length and thickness and such slubs are distributed at irregular intervals along the length of the yarn, and other portions of the multifilament yarn are re-bundled while travelling from the slub-forming device 4 to the take up package 9.

The multifilament yarns usable for the process of the present invention may be selected conventional natural and artificial multifilament yarns. The natural multifilament yarn may be a silk yarn. The artificial multifilament yarn may be a regenerated cellulose multifilament yarn, for example, viscose rayon or cuprammonium rayon yarn, regenerated protein multifilament yarn, semi-synthetic multifilament yarn, for example, cellulose diacetate or cellulose triacetate filament yarn, and synthetic multifllament yarn made of a fiber-forming synthetic polymer, for example, polyester such as polyethylene terephthalate, polybutylene terephthalate, polyoxyethylene benzoate or polyethylene terephthalate-type copolyesters containing isophthalic acid, phthalic acid, adipic acid, sebacic acid, diethylene glycol or polyethylene glycol and copolymers of these; polyamide such as nylon 6, nylon 66, nylon 610, nylon 12, polyamide including cyclohexane groups, polyamide including isophthalic acid, pthalic acid or terephthalic acid or these copolymer; polyamidoether; polyolefin such as polyethylene, polypropylene or ethylenepropylene copolymer; and acrylic polymer such as polyacrylonitrile or acrylonitrile copolymer.

It is desirable that the multifilament yarn usable for the present invention be easily opened by the action of the air vortex or turbulent current produced in the slub-forming device. For this purpose firmly twisted multifilament yarns are firmly bonded multifilament yarns with a sizing agent are not suitable because they are difficult to open. However, the firmly twisted and sized multifilament yarns may be used for the process of the present invention if at least one other multifilament yarn which can be easily opened, is used, as a slub-forming yarn, together with them.

Referring to FIG. 1, the feed means 3a and 3b for the multifilament yarn I feed the yarn at a constant rate without slippage of the yarn on the feed means. The feed means may be of any type, for example, a pair of nip rollers as shown in FIG. 1, apron rollers or Nelsons rollers.

The winding up means for the slub yarn may be a conventional winder capable of taking up the slub yarn at a desired constant rate. For the process of the present invention, a conventional RT winder having no transverse guide and traveller is preferable rather than a conventional spindle drive winder or QT winder which have the traverse guide and traveller. This is because the slubs formed on the slub yarn of the present invention tend to restrict passage of the yarn through the traverse guide and traveller. This is because the slubs have a larger thickness than that of the original multifilament yarn and, therefore, are frequently caught in the traverse guide and traveller.

The slub-forming device for forming therein the reduced pressure region, will be explained in detail by referring to FIGS. 2 through 9 of the accompanying drawings.

FIG. 2 shows a longitudinal cross-sectional view of a simple embodiment of the slub-forming device. The slub-forming device 11 has a hollow column 12, a yarn supply end plate 13 and a yarn delivery end plate 15. The yarn supply end plate 13 has a yarn supply hole 14 formed in the center of the plate 13. The yarn delivery end plate 15 has a yarn delivery hole 16 formed in the center of the plate 15. One end of an air suction pipe 17 is connected to a middle portion of the wall of the hollow column 12. The other end of the air suction pipe 17 is connected to a vacuum device (not shown in FIG. 2)

such as a vacuum pump.

When the vacuum device is actuated, the pressure of the hollow column 12 is reduced, and air is sucked at a high flow rate from the atmosphere through the yarn supply and delivery holes 14 and 16 into the hollow column 12. The air thus sucked generates under a reduced pressure an air vortex or turbulent current in the hollow column 12.

The multifilament yarn, together with the sucked air, is fed into the hollow column 12 through the yarn supply hole 14 and vigorously agitated by the action of the air current. During the agitating, portions of the multifilament yarn 1 are converted into slubs 7a distributed randomly along the yarn 7.

Sometimes, portions of the yarn 1 are sucked from the hollow column 12 into the air suction pipe 17 and converted into slubs having a relatively long length.

The hollow column 12 may have a circular cross-sectional profile or an irregular cross-sectional profile, for example, square, hexagonal, octagonal and oval crosssectional profiles.

In FIG. 3, the slub-forming device 21 is similar to the slub-forming device 1 1 shown in FIG. 2 except that the hollow column 12 is divided into two compartments by an air permeable partition 22. The partition 22 is perforated and has a plurality of small holes 23. The partition 22 is arranged parallel to the yarn travel path from the yarn supply hole 14 to the yarn delivery hole 16, between the yarn travel path and the end of the air suction pipe 17 connected to the wall of the hollow column 12. That is, one of the compartments is connected to the vacuum device (not shown in FIG. 3) through the air suction pipe 17 and the other compartment is connected to the atmosphere through the yarn supply and delivery holes 14 and 16. Only air, and not, the multifilament yarn can pass through the small holes 23 of the partition 22. The perforated partition 22 may be a to 100 mesh net.

When the vacuum device (not shown) is actuated, air is sucked from atmosphere through the yarn supply and delivery holes 14 and 16 into the hollow column 12 at a very high flow rate. A portion of the sucked air collides with the partition 22 and the other portion passes through the small holes 23 of the partition 22. The passing of the sucked air through the small holes 23 of the partition 22 causes suction of the multifilament yarn onto the surface of the partition 22 and the multifilament yarn temporarily stays on the partition surface 22. The collision of a portion of the sucked air with the partition 22 results in very vigorous agitation of the multifilament yarn which has been sucked onto the partition. While in the hollow column 12, the multifilament yarn l is prevented by the partition 22 from suction into the air suction pipe 17. This prevention is effective for promoting the formation of relatively uniform slubs in length, thickness and distribution. This is because the condition of the multifilament yarn staying in the slub-forming device 21 is relatively uniform throughout the operation time. In the embodiment of the apparatus as shown in FIG. 3, the hollow column preferably has an irregular cross-sectional profile, for example, square, hexagonal and octagonal cross-sectional profiles.

In FIG. 4, a slub-forming device 31 is similar to the slub-forming device 11 shown in FIG. 2 except that an air permeable partition 32 having a plurality of small holes 33 is arranged in the air suction pipe 17, and the yarn delivery end plate 15 has one or more air suction holes 34 in addition to the yarn delivery hole 16. Air suction holes 34 may also be formed in the wall 35 of the hollow column 12 or the yarn supply end plate 13. Since the hollow column 12 in FIG. 4 has three or more holes which allow suction of air therethrough, the slub forming device of FIG. 4 can suck air in an amount larger than the devices shown in FIGS. 2 and 3. Accordingly, the multifilament yarn .1 is easily sucked into the air suction pipe 17. In the pipe 17 the sucked multifilament yarn collides with the partition 32 and accumulates thereon. The accumulated multifilament yarn is vigorously agitated by the action of sucked air vortex. The agitated multifilament yarn is withdrawn from the partition 32 through the yarn delivery hole 16 in the opposite direction to that of the sucked air flow. This travel of the multifilament yarn promotes the slub formation by the action of the sucked air current in the opposite direction.

In the case of FIG. 4, the multifilament is sucked towards and accumulated on the partition 32 and the agitating action of the sucked air is weaker than in the cases of FIGS. 2 and 3. Therefore, the movements of the multifilament yarns, such as entanglement, intertwining, bending, folding, opening and looping, are relatively less than the cases of FIGS. 2 and 3. Accordingly, the slub yarn produced by the slub-forming device 31 of FIG. 4 has slubs which are larger in length but fewer in total number than the slub yarns of FIGS. 2 and 3.

Referring to FIG. 5, a slub-forming device 41 is provided with a yarn storage inner hollow column 42 concentrically located in the outer hollow column 12. The yarn storage inner hollow column 42 is fixed at its yarn supply end to the yarn supply end plate 13, and surrounds a portion of the yarn travel path between the yarn supply and delivery holes 14 and 16. That is, the yarn supply hole 14 opens into one end of the yarn storage inner hollow column 42, while the other end 44 of the yarn storage inner hollow column 42 is open to the outer hollow column 12. A plurality of holes 43 are formed at the yarn supply end portion of the wall of the yarn storage inner hollow column 42, to connect yarn supply end portion of the yarn storage inner hollow column 42 to the outer hollow column 12 and the air suction pipe 17. The yarn storage inner hollow column 12 may have a circular cross-sectional profile or an irregular cross-sectional profile, for example, square, hexagonal, octagonal and oval cross-sectional profile.

An air suction member 45 is located between the yarn delivery end plate 15 and the open end 44 of the yarn storage inner hollow column 42. There is a clearance 48 between the air suction member 45 and the yarn storage inner hollow column 42.

Referring to FIGS. 5 and 6, the air suction member 45 has a center opening 46 of the same diameter as the inside diameter of the yarn storage inner hollow column 42. The yarn travel path passes through the center opening 46 of the air suction member 45. The air suction member 45 is provided with one or more air suction holes 47 through which the center opening 46 is connected to the atmosphere. The air suction hole 47 is formed in such a manner that the longitudinal axis of the air suction hole 47 does not intersect the longitudinal axis of the center opening 46. The air suction holes 47 thus formed are effective for generating a vortex of the sucked air in the slub-forming device 41.

Referring to FIG. 7, the holes 43 are formed through the wall of the yarn storage inner hollow column 42 in such a manner that the longitudinal axes of the holes 43 do not intersect the longitudinal axis of the yarn storage inner hollow column 42. The holes 43 are effective for promoting the formation of vortex of the sucked air in the yarn storage inner hollow column 42. The holes 43 may be formed in such a manner that the longitudinal axes of the holes 43 intersect the longitudinal axis of the yarn storage inner hollow column.

When the vacuum device (not shown in FIG. is actuated, air is sucked from the atmosphere into the slubforming device 41 through the yarn supply and delivery holes 14 and 16 and the air suction holes 47 of the air suction member 45. The air sucked through the air suction holes 47 and the yarn delivery hole 16 is formed into a vortex in the center opening 46, and further sucked into the air suction pipe 17. The air sucked into the yarn storage inner hollow column 42 through the yarn supply hole 14 is further sucked into the suction pipe 17 through the holes 43 and also the opening 45 and clearance 48. Accordingly, in the yarn delivery end portion of the yarn storage inner hollow column 42, air flows upward'from the middle portion thereof and in the yarn supply end portion of the inner hollow column 42, air flows downward from the middle portion. That is, the sucked air in the yarn storage inner hollow column 42 is formed into two currents in opposite directions to each other. Therefore, the middle portion of the yarn storage inner hollow column 42 is reduced into a lower pressure than the other portions. In the middle portion, the turbulent air current is most vigorous. When the multifilament yarn l is fed into the yarn storage inner hollow column 42 through the yarn supply hole 14, the yarn 1 is vigorously agitated in the middle portion. While passing through the center opening 46 of the air suction member 45, the agitated yarn 1 is re-bundled by the air vortex.

Referring to FIG. 8, the slub-forming device 51 is provided with an air vortex inner hollow column 52 extending from the air suction member 45 toward the yarn storage inner hollow column 42. The hollow space of the air vortex inner hollow column 52 is connected with the center opening 46 of the air suction member 45. The end of the air vortex inner hollow column 52 facing the open end 44 of the yarn storage inner hollow column 42, is closed with an end member 53 having a funnel-shaped inside surface 54 and a hole 55 through which the yarn travels. Further, the air vortex inner hollow column 52 has a plurality of holes 56 formed in the side walls thereof. Referring to FIG. 9, the holes 56 are formed through the side walls of the air vortex inner hollow column 52 in such a manner that the longitudinal axes of the holes 56 do not intersect the longitudinal axis of the air vortex inner hollow column 52.

The multifilament yarn is vigorously agitated in the middle portion of the yarn storage inner hollow column 42, and travels into the air vortex inner hollow column 52 through the hole 55. The air vortex inner hollow column 52 strengthens the air vortex produced by the air suction member 45. Accordingly, while traveling through the air vortex inner hollow column 52 and the center opening 46 of the air suction member 45, the agitated yarn is re-bundled. That is, the slub-forming device 51 of FIG. 8 is effective for producing a compact slub yarn. The air vortex inner hollow column may be of a circular cross-sectional profile or an irregular cross-sectional profile, for example, square, hexagonal, octagonal and oval cross-sectional profiles.

The hollow column 12 and the yarn storage inner hollow column 42 wherein the slubs are formed, may have an inside wall surface containing sharply edged fine particles. Some of the individual filaments agitated in the slub-forming device come into contact with the abrasive surface containing the sharply edged particles and are broken. The broken filaments form fluffs on the yarn. Therefore, the resultant slub yarn has a spun slub yarn-like appearance but is made of the multifilament yarn.

The abrasive surface carries thereon numerous fine abrasive grains having a high hardness and sharp edges to scratch or break the filaments. The abrasive surface may be an abrasive sheet such as sand paper or sand cloth, on which numerous abrasive grains are fixed with a binder.

The abrasive grains preferably consist of a metallic material such as carbon steel quenched by high frequency induction process, or an inorganic material such as diamond, boron carbide, silicon carbide, crystallized alumina, molten zircon, garnet, jade and rock crystal, silica, molten quartz, orthoclase and apatite, or mixtures of two or more of these materials. The abrasive grains preferably have a size of 16 to 250 y. and are preferably distributed in a density of 50 grains/cm or more.

The slub-forming devices usable for the present invention are not limited to those as shown in FIGS 2 through 9. Rather, these FIGS. merely illustrate particular preferred embodiments of the present invention. It will be recognized that variations and modifications of the disclosed apparatus including the rearrangement of parts, lie within the scope of the present invention.

FIGS. 10 and 11 show explanatory views of slub yarns produced by the present invention, respectively. In FIG. 10, the slub is formed from complicately entangled, intertwined, folded and/or looped individual filaments separated from each other. In FIG. 11, the slub is formed by a portion of the yarn being folded and intertwined with itself.

In the process of the present invention, the pattern of the slub to be produced is in response to condition of the sucked air current under a reduced pressure and the overfeed ratio. The term overfeed ratio used here refers to a ratio in percent of the difference between the feed rate and the delivery rate of the multifilament yarn to the delivery rate.

The condition of the sucked air current depends on the type of the slub-forming device, and has an influence upon the configuration and length of the slubs. The overfeed ratio influences the frequency of the slub formation and length of the slub.

In the process of the present invention, the overfeed ratio may be varied within a range of from 5 to 300%. Accordingly, by adjusting the overfeed ratio and selecting the type of the slub-forming device, almost all pat- 9 terns of slub yarns can be obtained.

Depending upon the overfeed ratio, type of the slubforming device and degree of vacuum, sometimes, the resultant slub yarn has slubs formed by loosely entangling and intertwining the yarn and/or individual filaments. Such slubs are very bulky. Therefore, in the travelling of the slub yarn, the loosely formed slubs are frequently restricted by the yarn guide in a rewinding, weaving or knitting machine. The interruption results in breakage of the slub yarn. Accordingly, the slub yarn having such loosely formed slubs cannot be used for rewinding, weaving and knitting. In this case, the defect as stated above can be eliminated by the following methods:

I. Firmly re-bundling the slub yarn removed from the slub-forming device by blowing ajet of air onto the slub yarn.

2. Firmly bonding the slub yarn by applying a bonding agent, such as sizing agent and resin.

3. Tightening the slub yarn by passing through a high temperature zone to shrink the looped filaments and loosely entangled yarn and filaments.

Otherwise, in order to produce firmly bundled slub yarn, it is effective to lightly twist the multifilament yarn in a small number of twists before feeding it into the slub-forming device, to lightly interlace the individual filaments by blowing a jet of air onto the yarn before the slub-forming. The twisting and interlacing stated above are effective for controlling the opening of the multifilament yarn.

The multifilament yarn usable for the present invention may be composed of a single multifilament yarn or two or more component multifilament yarns. The component multifilament yarns may be the same as or different from each other. The different component multifilament yarns may be different in type of polymer, denier of the yarn or individual filament, number of individual filaments and type of process applied to the yarn. That is, the multifilament yarn may be a crimped yarn, textured yarn or regular yarn, or a doubled yarn of a crimped or textured yarn and a regular yarn. Also, the multifilament yarn may consist of two or more thermoplastic polymer component yarns different in melting point from each other. The slub yarn produced by the present invention may be further subjected to a crimping or texturing process such as stuffing crimping and false-twisting.

In the case where the slub yarn consists of two or more thermoplastic polymer yarns different in melting point from each other, the slub yarn may be heat treated at a temperature lower than the lighter melting point but not lower than the lower melting point of the yarns. By the heat treatment, the higher melting point yarn is firmly bonded by the melted lower melting point yarn.

As stated hereinbefore, energy efficiency of the process of the present invention is higher than the conventional slub-forming methods wherein a fluid jet is blown onto the yarn, because the slub-forming is effected in a reduced pressure region wherein the yarn and individual filaments can easily move. Further, the apparatus of the present invention involves no twisting means and mechanism for forming slubs at random which are necessary for the conventional slub forming apparatuses. Therefore, the apparatus of the present invention is very simple in structure and of low cost, and can be driven at a very high velocity.

10 The following examples are presented merely for the purpose of illustrating the present invention.

EXAMPLES l THROUGH 30 As shown in Table l, in Example 1, a polyethylene terephthalate multifilament yarn of 100 denier consisting of 48 filaments (100 d/48 f) was twisted at a twist number of 10 turns per meter (10 T/M). The twisted yarn was processed in the apparatus as shown in FIG. 1 having the slub-forming device as shown in FIG. 2 under conditions as shown in Table 1, columns 4, 5, 6 and 7. In Table 1, column 6, the term overfeed ratio" refers to a ratio in of the difference between the feed rate and delivery rate of the yarn for the slub-forming device to the delivery rate. The processed yarn had the properties as shown in Table 2. In Table 2, the term frequency in forming of slub refers to the number of slubs formed in a 100 m length of the processed yarn.

The same procedures as in Example 1 were repeated in Examples 2 through 4, respectively, using the slubforming device shown in FIGS. 3 through 5, under conditions detailed in Table I. The properties of the slubformed yarns in Examples 2 through 4 are shown in Table 2.

The same procedures as in Example 1 through 4 were repeated in Examples 5 through 30, under the conditions and using the yarn and the slub-forming device as shown for each example in Table l. The slub-formed yarns in Examples 5 through 30 had the properties shown in Table 2.

Referring to Tables 1 and 2, the processed yarns in Examples 1, 5, 9,10,11,15, l9 and 23, which had been slub-formed by the slub-forming device of FIG. 2, had slub lengths varying in a wide range.

The slub-formed yarns in Examples 2, 6, l2, 16, 20, 24 and 25 using the slub-forming device of FIG. 3 had relatively short and thick slubs. The yarns slub-formed in Examples 3, 7, 13, I7, 21, 26 and 27 using the slubforming device of FIG. 4 had relatively long and thin slubs. In Examples 4, 8, 14, I8, 22, 28, 29 and 30 using the slub-forming device as shown in FIG. 5, the processed yarns had relatively thin and short slubs which were slightly different, in thickness and appearance, from the non slub-forming portion of the yarn.

From Tables I and 2, it is clear that the process and apparatus of the present invention are applicable for all types in material of multifilament yarns because neither heat nor chemicals are used for the slub-forming. The patterns of the slubs formed by the process of the present invention vary, in length, thickness and configuration, in response to the type of slub-forming device used. Further, it should be noted that the process of the present invention is applicable to any type in configuration of regular multifilament yarns, textured yarns, composite yarns of regular yarn with textured yarn and composite yarns of two or more same or different types of textured yarns. That is, the patterns of the formed slubs can be varied simply by varying the type of slubforming device and the slub-forming condition. The slub yarns produced in Examples 1 through 30 were similar in weaving property to the conventional twisted 1 l 12 fabrics each had a very sot't feel to the hand because the Table Lcominued yarn was not twisted during the slub-forming process. Further, since the regular portions of the slub yarn are EX Mean Largest Frequellcy weavmg P length length in forming property filaments on somewhat dishevelled in parallel arrangement of the N f slubs of slubs f slubs f b i individual filaments by the action of the sucked air cur- (cm) (cm) rent, the fabrics had silk fabric-like luster due to desirnoticeable able diffused reflection of light at the regular portions 33 82 45 normal ll 105 53 normal of the slub yarns 1n the fabrics. 12 H 85 good H Some of the slub yarns in these examples had loops 13 23 79 3i slightly negligible 10 Poor formed by the dishevelled indlvldual filaments in the 14 4 6 220 good Slightly slubs and the regular portions of the yarns. noticeable Table 1 Ex. Starting yarn Slub- Feed Wind Over- Degree No. formrate up feed of ing (mlmin) rate ratio vacuum device (m/min) (mmHg) 1 Polyethylene terephthalate (PET) A 460 400 15 45 yarn I00 d/48 f,l0 TIM 2 H B H H H H 3 H C H H H H 4 H D H H H H 5 Cellulose diacetate yarn 150 d/3O f, 10 T/M A 420 350 20 6 H B H H H H 7 H C H H H H 8 H D H H H H 9 Nylon 66 yarn 75 d/36 f 10 TIM A 520 450 I5 50 10 Polyacrylonitrile yarn 1S0 d/48 f, 15 T/M A l l Cellulose diacetate yarn 150 d/3O f crimped by a gear crimping A 360 300 20 machine 2 H B H H H H 13 H C H H H H 14 H D H H H H 15 PET 150 11/30 f falsetwisted textured yarn and PET 50 d/24 f, A 455 350 30 50 1O T/M regular yarn is H B H H H H 7 H C H H H H [8 H D H H H H 19 PET 50 d/24 f, 10 TIM and cellulose di- A 495 450 I0 acetate yarn 100 d/ 24 f, 60 T/M 20 PET SO d/24 f, 10 T/M and cellulose di acetate yarn lOO d/ B 495 450 10 50 24 f, 60 T/M 2| H C H H H H 22 H D H H H H 23 PET I00 d/48 f,l0 T/M regular yarn A 440 400 I0 24 B H H H H 25 B 520 30 26 C 440 l0 27 C 520 30 28 D 440 l0 29 D 520 30 30 D 600 Note: A. B, C and D are slub-forming devices shown in Figs. 2, 3. 4 and 5. respectively.

15 35 125 63 slightly poor Table 2 l6 I0 30 l35 normal Ex. Mean Largest Frequency Weaving Looped 17 28 103 39 Slightly negligible length length in forming property filaments on P No of slubs of slubs of slubs fabric 18 5 14 275 good slightly (cm) (cm) noticeable l9 13 65 28 normal noticeable l 30 l08 38 normal slightly 0 20 8 25 57 good noticeable 21 17 120 30 normal negligible 2 15 25 good noticeable 22 4 I3 152 good very 3 31 I25 20 slightly negligible noticeable poor 23 13 65 29 good slightly 4 5 10 l good very noticeable noticeable 24 7 26 57 normal slightly 5 35 I00 51 normal slightly 65 noticeable noticeable 25 10 3O 92 normal noticeable 6 21 40 98 normal noticeable 26 15 I28 28 normal negligible 7 63 150 39 normal negligible 27 20 32 slightly 8 5 .8 IS 250 good noticeable poor 9 28 76 52 normal slightly 28 5 8 good slightly Table 2-continued Ex. Mean Largest Frequency Weaving Looped length length in forming property filaments on No. of slubs of slubs of slubs fabric noticeable 29 6 I3 293 good noticeable 30 6 65 I normal slightly noticeable EXAMPLES 31 THROUGH 33 In Example 31, the same procedures as in Example 1 were repeated using the same apparatus as shown in FIGS. 1 and 2 except that an interlace nozzle was arranged between the slub-forming device and the delivery roller 8 and compressed air of a 3 kg/cm pressure was ejected onto the slub-formed yarn through the interlace nozzle.

In Example 32, the same procedures as in Example 31 were repeated using, instead of the interlace nozzle, a rotatable sizing roller located between slub-forming device and the delivery roller 8. A lower portion of the sizing roller was immersed in a bath containing an aqueous solution of 3% by weight of polyvinyl alcohol. The slub-formed yarn delivered from the slub-forming device was brought into contact with an upper portion of the sizing roller, carrying on its periphery surface a polyvinyl alcohol solution, and sized.

In Example 33, the same procedures as in Example 31 were repeated using, instead of the interlace nozzle, a hot plate of a l in length placed between the slubforming device and the delivery roller. The hot plate was heated at a temperature of 230C, and the slub formed yarn delivered from the slub-forming device came into contact with the heating surface of the hot plate. The resultant slub yarns in Examples 31 through 33 were remarkably improved in the bundling of the individual filaments in the slub portions and the regular portions of the slub yarns. That is, in these slub yarns dishevelling of the individual filaments was prevented. This is similar to the conventional twisted slub yarns.

The slub yarn of Example 31 had small loops of the filaments. However, the processability in weaving and knitting of the slub yarn was similar to that of the regular multifilament yarns. The slub yarns of Examples 32 and 33 had much less filament loops and were similar in processability to the regular yarns.

Further, it should be: noted that even in the cases where the interlace nozzle, sizing roller or hot plate was located between the slubforming device was the delivery roller to bundle the individual filaments in the slub yarn, the resultant slub yarn had no change in slub pattern, that is, frequency in slub forming and length and thickness of the slubs.

Additionally, the same procedures as in Examples 31 through 33 were repeated using the same starting yarn under the same process conditions as those in Examples 2, 3, 4, I9, 20, 21 or 22. All of the procedures were carried out without difficulty, and the resultant slub yarns were improved in bundling of the individual filaments.

EXAMPLES 34 THROUGH 41 The same slub yarns as produced in Examples 1 through 4 and 19 through 22 were crimped using a gear crimping machine having a heater device located upstream of the crimping gear. The crimped slub yarns were used to produce fabrics. The resultant fabrics had a high bulkiness and very soft feel to the hand. The heater device located upstream of the crimping gear was effective for improving the bundling of the individual filaments in the slub yarns. Therefore, the crimped slub yarns were woven into uniform fabrics without difficulty.

The same procedures as in Examples 34 through 41 were repeated using, instead of the gear crimping machine, a frictional false-twisting device. The resultant fabrics were highly bulky and very soft. The false-twisting device was provided with a heater located upstream from a friction drive means. The heater was effective for bundling the individual filaments in the slub yarns.

EXAMPLES 42 THROUGH 49 An interlace nozzle was located upstream of the feed roller in the apparatus shown in FIG. 1. In Example 42, the same procedures as in Example 1 were repeated using the above-mentioned apparatus. Before the slubforming step, the starting yarn was lightly bundled by the action of a compressed air current spouted through the interlace nozzle under a pressure of 0.5 kg/cm. The processed yarn had the properties as shown in Table 3.

In Examples 43 through 49, the same procedures as in Examples 2 through 4 and 19 through 22, respectively, were repeated using the above-mentioned apparatus. The properties of the resultant slub yarns are shown in Table 3.

Table 3 Ex. Starting yarn Slub-yarn No. and process conditions Mean Largest Frequency Weaving Loop length length in slubproperty form of of slubs forming ing slubs (cm) m) 42 as Example I 41 26 slightly ordinal poor 43 as Example 2 26 41 53 normal ordinal 44 as Example 3 40 I53 14 slightly poor less 45 as Example 4 6 I9 113 normal ordinal 46 as Example 19 IS 38 19 slightly poor less 47 as Example 20 I0 37 24 normal ordinal 48 as Example 21 20 l35 l3 slightly poor less 49 as Example 22 5 15 good ordinal The spouting of the compressed air resulted in slightly bundling the individual filaments in the starting yarn. The bundling caused difficulty in the opening of the individual filaments in the slub-forming step. Less opening of the individual filaments resulted in less entanglements, intertwinings and loopings of the individual filaments. Accordingly, Table 3 shows that the resultant slub yarns had less frequency of slub-forming and larger slub length than those in Examples 1 through 4 and 19 through 22. Further, the loopformation in Examples 42 through 49 was less than in the corresponding foregoing examples. Therefore, the slub yarns obtained in the present examples had regular (non slubformed) portions similar in appearance to the starting yarn.

EXAMPLE 50 A hot plate of a l m length was inserted between the slub-forming device and the delivery roller in apparatus shown in FIG. 1. The hot plate was maintained at a temperature of 170C to heat the slub yarn delivered from the slub-forming device.

A polyethylene terephthalate multifilaments yarn of a 300 denier consisting of 36 filaments and having a twist number of 10 T/M was doubled with a polypropylene yarn of denier consisting of 7 filaments and having a twist number of 10 T/M and the doubled yarn was fed into the above-stated apparatus having slub-forming device as shown in FIG. 5 to convert it into a slub yarn. The fed doubled yarn was processed under the following conditions.

Feed rate 345 m/min Wind-up (delivery) rate 300 m/min Degree of vacuum 50 mml-Ig Heater temperature 170C When the doubled yarn came into contact with the heater plate, the polypropylene yarn was melted in parts and bonded the individual polyethylene terephthalate filaments and the remaining polypropylene filaments in the slub yarn. The loops formed on the slub yarn were shrunk by the contact with the heater plate. Accordingly, the resultant slub yarn has a high processability in winding, weaving and knitting.

The same procedures as in the present example were repeated using, instead of the slub-forming device of FIG. 5, the slub-forming device of FIGS. 2, 3 and 4. The resultant slub yarns were similar in processability to the yarn in the present example.

What we claim is:

1. A process for continuously producing slub yarns comprising the steps of:

providing a reduced pressure region in a closed hollow column and connected to the atmosphere through a yarn supply hole at an end of said column and a yarn delivery hole located at an opposite end of said column, by sucking air from the atmosphere through said region;

feeding a multifilament yarn into said reduced pressure region through said yarn supply hole at predetermined feed rate while sucking air through said region;

agitating said fed multifilament yarn in said reduced pressure region by action of the sucked air current in order to convert portions of said multifilament yarn into slubs; and

delivering said resultant slub yarn from said reduced pressure region through said yarn delivery hole at a delivery rate lower than said feed rate.

2. A process as claimed in claim 1, wherein said fed multifilament yarn is sucked onto an air-permeable surface provided within said reduced pressure region.

3. A process as claimed in claim 2, wherein said fed multifilament yarn temporarily stays on said air-permeable surface.

4. A process as claimed in claim 1, wherein said sucked air is formed into two currents in opposite directions to each other within said reduced pressure region.

5. A process as claimed in claim 1, wherein said slub yarn delivered from said reduced pressure region is rebundled by the action of an air jet blown onto the slub yarn.

6. A process as claimed in claim 1, wherein said slub yarn delivered from said reduced pressure region is bonded by applying a bonding agent to the slub yarn.

7. A process as claimed in claim 1, wherein said slub yarn delivered from said reduced pressure region is tightened by heating it at a temperature at which the looped or loosely entangled individual filaments shrink.

8. A process as claimed in claim 1, wherein said multifilament yarn is lightly bundled before feeding it into said reduced pressure region.

9. A process as claimed in claim 1, wherein said multifilament yarn is a crimped or textured yarn.

10. A process as claimed in claim 1, wherein said multifilament yarn consists of two or more component multifilament yarns.

11. A process as claimed in claim 10, wherein said component yarns are the same.

12. A process as claimed in claim 10, wherein said component yarns are different from each other.

13. A process as claimed in claim 12, wherein said component yarns are one or more crimped multifilament yarns and one or more regular multifilament yarns.

14. A process as claimed in claim 12, wherein said component yarns are thermoplastic polymer multifilament yarns different in melting point from each other.

15. A process as claimed in claim 14, wherein said slub yarn consisting of said thermoplastic polymer multifilament yarns different in melting point from each other, is heat treated at a temperature lower than the higher melting point but not lower than the lower melting point of said thermoplastic polymer multifilament yarns.

16. A process as claimed in claim 1, wherein a ratio of difference between said feed rate and said delivery rate to said delivery rate is in a range from 5 to 300%.

17. A process as claimed in claim 1, wherein said yarn is, after slub-forming, further re-bundled within said reduced pressure region by action of a vortex of the sucked air.

18. A process as claimed in claim 1, wherein said yarn travels upward.

19. An apparatus for continuously producing a slub yarn from a multifilament yarn, comprising:

a slub-forming device comprising a closed hollow column having a yarn supply plate located at an end of said column and having a yarn supply hole formed thereon and a yarn delivery plate located at an opposite end of said column and having a yarn delivery hole formed thereon;

1'7 feed means for feeding a multifilament yarn at a predetermined feed rate into said slub-forming device through said yarn supply hole; delivery means for deliverying a slub-yarn at a predetermined delivery rate lower than said feed rate from said slub-forming device through said yarn delivery hole, and;

means for sucking air from the atmosphere through said slub-forming device, said means being connected to the periphery of said hollow column.

20. The apparatus of claim 19 wherein said means for sucking air is connected to the periphery of said hollow column by a pipe.

21. An apparatus as claimed in claim 20, wherein said pipe is provided with an air permeable partition located therein.

22. An apparatus as claimed in claim 19, wherein said hollow column has a circular cross-sectional profile.

23. An apparatus as claimed in claim 19, wherein said hollow column has an irregular cross-sectional profile.

24. An apparatus as claimed in claim 19, wherein said hollow column of said slub-forming device is divided into two compartments with an air permeable partition disposed in parallel to the yarn travel path from the yarn supply hole to the yarn delivery hole, between the yarn travel path and the entrance of said air suction means.

25. An apparatus as claimed in claim 24, wherein said hollow column has a square cross-sectional profile.

26. An apparatus as claimed in claim 19, wherein said hollow column of said slub-forming device has a yarn storage inner hollow column located therein and surrounding the yarn travel path between said yarn supply hole and the yarn delivery hole, said yarn storage inner hollow column having a yarn supply end connected to the yarn supply end plate of said hollow column, the other end opening in said hollow column and a plurality of small holes formed on the yarn supply end portion thereof.

27. An apparatus as claimed in claim 26, wherein said small holes on said inner hollow column are formed in such a manner that the longitudinal axes of said holes do not intersect the longitudinal axis of said yarn storage inner hollow column.

28. An apparatus as claimed in claim 26, wherein said small holes on said inner hollow column are formed in such a manner that the longitudinal axes of said holes intersect the longitudinal axis of said yarn storage inner hollow column.

29. An apparatus as claimed in claim 26, wherein said hollow column further comprises an air suction member located between said yarn delivery end plate and said yarn storage inner hollow column and having a center opening and one or more air suction holes through which said center opening is connected to at mosphere, said air suction holes being formed in such a manner that the longitudinal axes of said air suction holes do not intersect with the longitudinal axis of said center opening.

30. An apparatus as claimed in claim 29, wherein said hollow column of said slub-forming device is further provided with an air vortex inner hollow column extending from said air suction member toward said yarn storage inner hollow column and surrounding said yarn travel path, said air vortex inner hollow column having a plurality of small holes formed on its periphery in such a manner that the longitudinal axes of the holes do not intersect with the longitudinal axis of the air vortex inner hollow column, and a hole formed on its one end facing said yarn storage inner hollow column.

31. An apparatus as claimed in claim 26, wherein said yarn storage inner hollow column has an inside wall surface containing sharply edged fine particles.

32. An apparatus as claimed in claim 19, wherein said hollow column has an inside wall surface made of sharply edged fine particles. 

1. A process for continuously producing slub yarns comprising the steps of: providing a reduced pressure region in a closed hollow column and connected to the atmosphere through a yarn supply hole at an end of said column and a yarn delivery hole located at an opposite end of said column, by sucking air from the atmosphere through said region; feeding a multifilament yarn into said reduced pressure region through said yarn supply hole at predetermined feed rate while sucking air through said region; agitating said fed multifilament yarn in said reduced pressure region by action of the sucked air current in order to convert portions of said multifilament yarn into slubs; and delivering said resultant slub yarn from said reduced pressure region through said yarn delivery hole at a delivery rate lower than said feed rate.
 2. A process as claimed in claim 1, wherein said fed multifilament yarn is sucked onto an air-permeable surface provided within said reduced pressure region.
 3. A process as claimed in claim 2, wherein said fed multifilament yarn temporarily stays on said air-permeable surface.
 4. A process as claimed in claim 1, wherein said sucked air is formed into two currents in opposite directions to each other within said reduced pressure region.
 5. A process as claimed in claim 1, wherein said slub yarn delivered from said reduced pressure region is rebundled by the action of an air jet blown onto the slub yarn.
 6. A process as claimed in claim 1, wherein said slub yarn delivered from said reduced pressure region is bonded by applying a bonding agent to the slub yarn.
 7. A process as claimed in claim 1, wherein said slub yarn delivered from said reduced pressure region is tightened by heating it at a temperature at which the looped or loosely entangled individual filaments shrink.
 8. A process as claimed in claim 1, wherein said multifilament yarn is lightly bundled before feeding it into said reduced pressure region.
 9. A process as claimed in claim 1, wherein said multifilament yarn is a crimped or textured yarn.
 10. A process as claimed in claim 1, wherein said multifilament yarn consists of two or more component multifilament yarns.
 11. A process as claimed in claim 10, wherein said component yarns are the same.
 12. A process as claimed in claim 10, wherein said component yarns are different from each other.
 13. A process as claimed in claim 12, wherein said component yarns are one or more crimped multifilament yarns and one or more regular multifilament yarns.
 14. A process as claimed in claim 12, wherein said component yarns are thermoplastic polymer multifilament yarns different in melting point from each other.
 15. A process as claimed in claim 14, wherein said slub yarn consisting of said thermoplastic polymer multifilament yarns different in melting point from Each other, is heat treated at a temperature lower than the higher melting point but not lower than the lower melting point of said thermoplastic polymer multifilament yarns.
 16. A process as claimed in claim 1, wherein a ratio of difference between said feed rate and said delivery rate to said delivery rate is in a range from 5 to 300%.
 17. A process as claimed in claim 1, wherein said yarn is, after slub-forming, further re-bundled within said reduced pressure region by action of a vortex of the sucked air.
 18. A process as claimed in claim 1, wherein said yarn travels upward.
 19. An apparatus for continuously producing a slub yarn from a multifilament yarn, comprising: a slub-forming device comprising a closed hollow column having a yarn supply plate located at an end of said column and having a yarn supply hole formed thereon and a yarn delivery plate located at an opposite end of said column and having a yarn delivery hole formed thereon; feed means for feeding a multifilament yarn at a predetermined feed rate into said slub-forming device through said yarn supply hole; delivery means for deliverying a slub-yarn at a predetermined delivery rate lower than said feed rate from said slub-forming device through said yarn delivery hole, and; means for sucking air from the atmosphere through said slubforming device, said means being connected to the periphery of said hollow column.
 20. The apparatus of claim 19 wherein said means for sucking air is connected to the periphery of said hollow column by a pipe.
 21. An apparatus as claimed in claim 20, wherein said pipe is provided with an air permeable partition located therein.
 22. An apparatus as claimed in claim 19, wherein said hollow column has a circular cross-sectional profile.
 23. An apparatus as claimed in claim 19, wherein said hollow column has an irregular cross-sectional profile.
 24. An apparatus as claimed in claim 19, wherein said hollow column of said slub-forming device is divided into two compartments with an air permeable partition disposed in parallel to the yarn travel path from the yarn supply hole to the yarn delivery hole, between the yarn travel path and the entrance of said air suction means.
 25. An apparatus as claimed in claim 24, wherein said hollow column has a square cross-sectional profile.
 26. An apparatus as claimed in claim 19, wherein said hollow column of said slub-forming device has a yarn storage inner hollow column located therein and surrounding the yarn travel path between said yarn supply hole and the yarn delivery hole, said yarn storage inner hollow column having a yarn supply end connected to the yarn supply end plate of said hollow column, the other end opening in said hollow column and a plurality of small holes formed on the yarn supply end portion thereof.
 27. An apparatus as claimed in claim 26, wherein said small holes on said inner hollow column are formed in such a manner that the longitudinal axes of said holes do not intersect the longitudinal axis of said yarn storage inner hollow column.
 28. An apparatus as claimed in claim 26, wherein said small holes on said inner hollow column are formed in such a manner that the longitudinal axes of said holes intersect the longitudinal axis of said yarn storage inner hollow column.
 29. An apparatus as claimed in claim 26, wherein said hollow column further comprises an air suction member located between said yarn delivery end plate and said yarn storage inner hollow column and having a center opening and one or more air suction holes through which said center opening is connected to atmosphere, said air suction holes being formed in such a manner that the longitudinal axes of said air suction holes do not intersect with the longitudinal axis of said center opening.
 30. An apparatus as claimed in claim 29, wherein said hollow column of said slub-forming device is further provided with an air vortex inner hollow column extending froM said air suction member toward said yarn storage inner hollow column and surrounding said yarn travel path, said air vortex inner hollow column having a plurality of small holes formed on its periphery in such a manner that the longitudinal axes of the holes do not intersect with the longitudinal axis of the air vortex inner hollow column, and a hole formed on its one end facing said yarn storage inner hollow column.
 31. An apparatus as claimed in claim 26, wherein said yarn storage inner hollow column has an inside wall surface containing sharply edged fine particles.
 32. An apparatus as claimed in claim 19, wherein said hollow column has an inside wall surface made of sharply edged fine particles. 